I had faced problems in creating a same copy of the VB system .
I tried to do by creating a copy of the hard disk and adding it to the environment. This will not work since the copied will has the same hard disk identification of the source .
I was able to solve this issue using the command “VBoxManage clonevdi ”
you need to give the full path for the files eg
VBoxManage clonevdi /home/itsupport/.VirtualBox/HardDisks/PBX1.vdi /home/itsupport/.VirtualBox/HardDisks/PBX2.vdi
, otherwise it will throw an error